[ fee-aht, -at; fahy-uh t, -at ]
/ ˈfi ɑt, -æt; ˈfaɪ ət, -æt /


an authoritative decree, sanction, or order: a royal fiat.
a fixed form of words containing the word fiat, by which a person in authority gives sanction, or authorization.
an arbitrary decree or pronouncement, especially by a person or group of persons having absolute authority to enforce it: The king ruled by fiat.

Origin of fiat

1625–35; < Latin: let it be done, 3rd singular present subjunctive of fierī to become

Definition for fiat (2 of 3)

fiat justitia, ruat caelum
[ fee-aht yoo s-tee-tee-ah roo-aht kahy-loo m; English fee-aht juhs-tish-ee-uh roo-at see-luh m, fahy-uh t ]
/ ˈfi ɑt yʊsˈti tiˌɑ ˈru ɑt ˈkaɪ lʊm; English ˈfi ɑt dʒʌsˈtɪʃ i ə ˈru æt ˈsi ləm, ˈfaɪ ət /


let there be justice though the heavens fall.

Definition for fiat (3 of 3)

fiat lux
[ fee-aht loo ks; English fee-aht luhks, fahy-uh t ]
/ ˈfi ɑt ˈlʊks; English ˈfi ɑt ˈlʌks, ˈfaɪ ət /


let there be light. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for fiat

British Dictionary definitions for fiat

/ (ˈfaɪət, -æt) /


official sanction; authoritative permission
an arbitrary order or decree
mainly literary any command, decision, or act of will that brings something about

Word Origin for fiat

C17: from Latin, literally: let it be done, from fierī to become
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012